There are many nails in use including the common and finishing smooth shank nails, the ring shank nail for increased holding power beyond that of a common round nail, the deformed shank nail including the twisted square, rectangular, spiral or screw type grooved shank nail, triangular shaped nails and the hardened masonry nails. The above-mentioned nails are designed for various purposes but none accomplishes a substantial reduction in fastener material while substantially inhibiting lateral movement between a pair of wooden members connected by the fastener in accord with this invention. Also, the holding power of the nails of the prior art are not as effective as is often needed and none measures up to the holding power of the fastener in accord with this invention. Many of the nails of the prior art are furthermore wasteful as being fabricated from an excess of steel, aluminum or other metals which is of increasingly important competitive consideration.
The prior art nails are unsuitable in many wood constructions and when used often cause splitting of the wood along the grain. For example, a common round or square or rectangular nail when driven into wood tends to drive the grain apart or to split the same, creating a "fish-eye" condition of the grain around the nail shank. Thus, frictional contact between the common nail and the wood is less than complete and there is no tight fit about the shank thus reducing the holding power of the driven nail into the wood.
The fastener in accord with this invention overcomes many of the aforementioned problems of one or more of the prior art nails mentioned above and substantially alleviates all of the aforementioned shortcomings of the prior art as will be readily understood by consideration of the entire specification, drawings and claims herein.
The improved fastener in accord with several aspects of the invention is seen to include an elongated shank having opposite end portions and at least one longitudinal axis extending between the end portions, and an elongated central core with at least ten spaced elongated side walls forming with the core a cross-sectional shape of at least a five-pointed star. In a first embodiment of the invention, each adjacent pair of side walls taper toward each other and form a radial fin. One side wall of each pair of adjacent fins forms a vertically extending V-shaped cup having its valley juxtaposed to the core. The fins include elongated edges extending substantially parallel to the longitudinal axis and terminate outwardly generally equally from the longitudinal axis. The edges are rounded to inhibit breakage thereof during driving of the fastener into material. The sides forming the cups receive therein compressible material into which the fastener is drivingly disposed to compress material in the cups between the sides to enhance the holding power of the fastener in the material. The material is compressed downwardly and laterally into the cups to increase the holding power of the fastener in the material. The sides of the cups are substantially planar with the sides of radially adjacent fins being generally perpendicular. A valley having a curved surface integral with the core is formed between the adjacent side walls of radially adjacent pair of fins with the angle therebetween being substantially perpendicular. The edges of the fins have a radial dimension from the core at least equal to the diameter of the core.
In an alternate form, the fastener includes another shank having another longitudinal axis substantially parallel to the longitudinal axis and a bridging portion therebetween forming a head therefor to be driven as a staple. Preferably, the shank has a cross-sectional shape of at least a five-pointed star. The fastener may have one end portion tapered at an angle less than fourteen degrees to enhance the holding power of the fastener in material. A head is often provided on the other end portion for driving same with a hammer or the like into material and often a point is provided on the other one end portion. The shank is contemplated to be substantially uniformly tapered from the smaller dimension at one end portion to the other end portion at an angle less than fourteen degrees to enhance the holding power of the fastener in material such as a roof or concrete.
In yet another alternate form, the fastener includes shoulder means in the cups spaced along the shank to further enhance the holding power thereof. When the fastener includes a tapered portion the shoulder means in the cups may be spaced along only the tapered portion of the shank or the entire shank. The shoulder means are provided in at least three of the cups but may be provided in all of the vertical cups. The shoulder means extend or protrude outwardly away from the longitudinal axis. The shoulder means preferably are located at the core and the facing side walls and merge flush with the core and the facing side walls of the fins. In yet other alternative aspects the shank may include six, seven or more fins; the respective cross-sectional shape being a commensurate pointed star.
The final embodiment of this invention employs no more materials than the first embodiment, yet provides an increased surface area and increased tensile strength vis a vis said first embodiment. The diameter of the central core of the fastener of the final embodiment is reduced relative to the central core of the first embodiment, and the "saved" material is added to the fins so that said fins extend radially further from the longitudinal axis of the fastener.
Moreover, the sidewalls of the final embodiment are parallel to one another, as distinguished from the converging side walls of the first embodiment. The angle between adjacent fins (the fin-included angle) is reduced from the 98 degree angle of the first embodiment to 72 degrees in the final embodiment. It is believed that said respective angles represent the optimal upper and lower limits, respectively, for the angle between the fins. Fin-included angles beyond said upper and lower limits result in bulbous or scalloped fins, respectively.
The fastener core and fins radially extending therefrom in accord with the invention provide an increased outer surface area over that of a common round nail of a radius equal to the distance of the fastener from the longitudinal axis to one of the edges. It also provides easier drivability and superior holding power over other known hammerable fasteners. Each cup extends throughout substantially the length of the shank to form an elongated cupping means into which fibers of a pair of wooden members will be compressed downwardly and laterally during driving of the fastener into a pair of wooden members. This configuration substantially inhibits lateral movement between a pair of wooden members into which the fastener connects and enhances the holding power thereof.
The improved fastener end portions and at least one longitudinal axis extending between includes at least five equally spaced narrow fins extending radially outwardly from the core of a predetermined cross-section and extend substantially parallel to the longitudinal axis of the core. The fins include elongated edges extending in the same direction as the longitudinal axis with each adjacent pair of fins forming a vertically extending V-shaped cup having its valley juxtaposed to the core. The side walls compress compressible material downwardly and laterally into the V-shaped cups to increase the holding power of the fastener in material beyond that of prior art fasteners while substantially reducing the amount of material forming the fastener.
It is an object of this invention to advance the art of nail making in a pioneering manner by providing nails that use only about half the materials required to make a common round shank nail while increasing tensile strength and surface area without appreciably sacrificing ductility.
Another object is to advance the art by not only disclosing five pointed, star cross-sectional nails that achieve the first-mentioned object, but to teach the art the upper and lower limits of the angles between the fins that form a part of the improved nail.
The invention accordingly comprises the features of construction, combination of elements and arrangement of parts that will be exemplified in the construction hereinafter set forth and the scope of the invention will be indicated in the claims.